imaging exam 1 Flashcards
which types of imaging are non-ionizing?
ultrasound and MRI
which type of imaging is emission?
bone scan
on x-ray what is dark?
air, fat, water
on x-ray what is light?
metal, bone
position vs. projection
position: pt (recumbent vs. weight bearing)
projection: direction of beam
orthogonal imaging
2 images at least 90 degrees apart
radiograph search pattern
A: alignment
B: bone density
C: cartilage space
S: soft tissue
measuring units of CT
hounsfield unit
indications of CT
- hidden fracture
- high risk trauma
- loose bodies in joint
- degenerative changes in spine
contraindications of CT
- no absolute
- based on radiation
CT vs. MRI
- CT cheaper
- CT faster
- CT less expensive
- CT less claustrophobic
- MRI less radiation
MRI contraindications
- cardiac pacemakers
- orthopedic hardware
- iron in the pigments
- unknown safety for fetus
- any other ferrous implants
T1 vs. T2
T1: anatomy
T2: pathology, H2O, water
is MRI good at soft tissue or bone?
excellent for soft tissue, not good at bone
MRI search patterns
A – Alignment of anatomy
-Continuity of ligaments, nerves, and muscle
B – Bone signal
-Look for alteration in bone signal
C – Cartilage
-OCD deformities and articular cartilage alterations
D – eDema
-“Footprint for injury”
S – Soft Tissue and Synovial tissue
-Disorder of the synovium, fat pads, bursae, etc.
hyperechoic
bright white on US
hypoechoic
black on US
nuclear imaging (bone scan)
application of radioactive substances for the diagnosis and treatment of disease
what can detect Paget’s disease
bone scan
PET scan
used to detect metastasis or other metabolic processes
DEXA
measures bone density and body composition
fracture risk assessment tool (FRAX)
used for probability of hip fracture
who gets surgical neck fracture
older adults
who gets humeral head fractures
children
ACR guidelines
- Radiographs = Typically first image of choice
- MR = Neg radiographs and suspect soft tissue injury. Preferred for stress fractures
- CT = Used to best visual occult fracture and for surgical planning as well as soft tissue.
- US = superficial soft tissue diagnosis, especially to see dynamic subluxations.
- US Septc Arthritis = US Centesis.
X-ray views of shoulder
APER
APIR
Axillary
y view
MRI/CT shoulder views
axial
oblique sagittal
oblique coronal
who gets supracondylar fractures?
second most common fracture in children
who gets radial head fractures?
adults
who gets olecranon fractures?
people in MVA, trauma
who gets elbow dislocation?
adults get ulnar
children get radial
which salter Harris fracture is most common?
type 2 S: straight across A: above L: low T: through ER: crush/erasure
valgus extension overload of the elbow causes
osteochondritis dessicans of the capitulum and medial apophysitis (little leaguers elbow)
elbow fracture clinical prediction rule
elbow extension –> unlikely to have a fracture
images are magnified when they are ____ the board
farther away
visibility
contrast resolution
- for this you need both appropriate brightness and contrast
accuracy
spatial resolution
-spatial resolution and distortion
noise
unwanted fuzzinesss of the image, visible as brightness fluctuations, too few x-ray photons, more visible in digital images
artifacts
things on detector or something the pt. is wearing
- scatter
- foreign bodies
- digital specific artifacts
- performance of electronic detectors
digital images use ____ radiation than film
less
also able to edit values after
brightness
amount of luminance (light emission) of a display monitor
image contrast
differences in brightness levels or densities
higher atomic number = ______ x-ray absorption
higher
subject contrast
result of the absorption characteristics of the anatomic tissues
limbs: high subject contrast
abdomen = lower subject contrast ( more greyscale)
more penetrating power = ____ kV
increased
contrast resolution
an imaging receptor’s ability to distinguish between objects similar in subject contrast
grey scale
number of different shades of grey that can be stored
short scale
high conrast, few densities, but great difference between the,
long scale
large number of densities but few differences between them
spatial resolution
THINK DETAIL wanting accurate anatomic features with the greatest amount of sharpness
machines have different amounts of Line pairs per mm
motion
voluntary and involuntary (heartbeat, peristalsis)
distortion
misrepresentation of size or shape
SID
source of radiation to detector
OID
object to the detector distance
get greater size distortion
types of shape distortion
elongation
foreshortening
scatter
unwanted exposure (or fog) to the image bounces off of the patient, provides no useful information, reduces image contrast
quality
measurement of the penetrating power of the x-ray photons
more photons = better quality of beam
mA
quantity of x-rays, intensity of beam
Kv
greater the potential difference across the tube, the faster the electrons move
longer exposure
greater beam intensity
distance from source
farther away = decrease in intensity of beam
distance doubled = intensity 1/4
positive artifact
white on image
negative artifact
dark on image
overexposed
burnout, dark
what identification markers are needed?
patient identifcation markers
anatomic side markers
situs inversus
organs are backwards lol
which metal is best as far as hardening
titanium
intrinsic vs. extrinsic factors for MRI
intrinsic:
there are new radiation measurements, which ones?
exposure –> air kerma: overall intensity (similar to rankin)
absorbed dose–> gray: absorbed by pt
effective dose–>sievert: from scatter onto
radioactivity –>Becquerel
radiosensitivity
probability of damage by tissue type
non-stochastic radiation effects
occur only once a threshold of exposure has been exceeded
stochastic effects of radiation
don’t know, any amount of radiation can have the negative effect
accepted values of relative rist
entire population: 5.5-6.0%
adult only: 4.1-4.8%
radtiation induced cancer mortality risk in children is ____ times higher
3-5x
what does the collinator on the DXA help with?
majorly decreases scatter
low vs. high energy beams
low: bone
high: fat
pencil beam is ____ radiation, and _____ accurary
low, low
fan beam is ____ radiation, and _____ accuracy
high, high
which is more influenced by hormones cortical or trabecular bone?
trabecular
what compartments can the DXA see?
fat
bone
bone free lean tissue
android to gyroid ratio for females and males
females: less than 0.8
males: less than 1
side to side bone weight difference that is acceptable?
0.5 lbs
